[Graeme Dice]

Originally posted by alexi:
is the general strategy for recruiting tons of blood slaves to pick poor provinces with little income and just ignore the unrest that builds up?

You can't ignore unrest, as a 1d400 must be less than the current unrest level for the hunt to be successful. The complete rules for blood hunting are found in this thread:
Blood Hunting Mechanics

You'll need to deal with unrest some way. Whether this is through lowering taxes to 0 in a province and only putting 2-4 hunters in it, or patrolling a province and killing the population, then moving on is up to you.

and how useful are blood sacrafices (is it a necessity for those races that have it or just an advantage in spreading dominion faster)

Mictlan must perform blood sacrifices to spread its dominion at all. The other nations have it as an extra option that they can use when needed.